This invention relates generally to computer-based systems for navigating aircraft and, more particularly, to a system and method for detecting and responding to unanticipated threats to aircraft.
In planning the route of an aircraft's mission, known threats such as hostile ground fire, military bases, etc., are taken into account. The planned route, which is stored in the aircraft's computer system, includes a starting point, a number of intermediate waypoints, and an ending point. The distance between each waypoint is measured in nautical miles and is referred to as a leg. Thus, a planned route consists of a number of connected legs that angle around known threats to provide the shortest and safest route between the aircraft's starting point and its ultimate mission destination (endpoint). The route is planned such that there is no "threat intervisibility," i.e., the aircraft being detectable by the threat.
However, the route planning must also take into account the problem of unplanned threats, unknown at the time, which might "pop up" during the mission. When an unknown threat appears, steps must be taken to avoid detection by the threat without compromising the mission's objectives.
Prior approaches to this problem are too inflexible. When an unknown threat pops up during a mission, the aircraft's computer system automatically directs the aircraft to change course and steer along one of a number of predetermined evasive legs. While the aircraft is changing course, the system attempts to recognize the threat and to calculate the intervisibility of the threat. If the planned route intersects the threat's intervisibility, then a route change is calculated from the end of the evasive leg to the next waypoint. If the proposed route change still intersects the threat's intervisibility, then a second route change is calculated from the end of the evasive leg to the following waypoint, and so forth. However, this approach is too mechanical. It limits the options of the aircraft operator, forces evasive maneuvers that are not optimized for the unknown threat, and is often too slow.
An object of the invention, therefore, is to provide an improved method for an airborne aircraft to respond to an unanticipated threat. More specifically, an object of the invention is to provide a system and method that rapidly responds to unknown threats in a timely and safe manner. With the method of the invention, quick decisions are made when required for close-range threats, yet the aircraft operator is given maximum flexibility to choose a response when time permits.